In the short term, the authorities should consider installing more advanced sensors here and modify the air pollution index to better monitor and reflect the haze's health impact.

Scientists gave these assessments when The Straits Times asked them how Singapore could better prepare for the haze.

Last month, raging fires in Indonesia led to the worst haze in Singapore's history.

On Monday, Minister for the Environment and Water Resources Vivian Balakrishnan said Singapore will tap new satellite feeds by 2015 to provide early haze alerts, but scientists said this could be easier said than done.

Satellites look at the ground in different ways, and cross different places at different times, said Assistant Professor Jason Cohen from the National University of Singapore (NUS). He specialises in climate change computer models and is researching the haze.

For example, the Modis satellite passes over the region several times a day and can "see" several thousand kilometres at once, but its cameras' observations can be blocked by clouds. It may also mistake thick smoke for a cloud.

The Calipso satellite shines a laser beam that can cut through most clouds to pick up images. The thicker the smoke, the more energy is removed from the beam returned to the satellite.

But the beam's thinness means its horizontal visual range is at most 1km, and the satellite passes over the region more slowly.

Both satellites are operated by the US National Aeronautics and Space Administration (Nasa). The National Environment Agency (NEA) uses data from several satellites including Modis ones and Nanyang Technological University's X-Sat satellite.

"If you want to integrate information from different satellites to come up with a prediction, you must have a computer programme that can cover different scales in space and time, and different physical and chemistry data collected by the satellites. It's very challenging," said Dr Cohen.

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Haze continues to hover at dangerous levels on June 20Click on thumbnail to view (Photos: ST, TNP, The Star, AFP, Reuters)